Abstract
Betulin (BT), a pentacyclic lupine-type triterpenoid natural product, possesses antitumor activity in various types of cancers. However, its clinical development was discouraged due to its low biological activities and poor solubility. We prepared lup-20(29)-en-3β,28-di-yl-nitrooxy acetate (NBT), a derivative of BT, that was chemically modified at position 3 of ring A and C-28 by introducing a NO-releasing moiety. This study mainly explored the mechanism of NBT in treating breast cancer through the crosstalk between apoptosis and autophagy in mitochondria. NBT possessed a potent antiproliferative activity in MCF-7 cells both in vitro and in vivo. Mechanically, NBT affected cell death through the mitochondrial apoptosis pathway and autophagy. NBT induced cell cycle arrest in the G0/G1 phase by decreasing the expression of cyclin D1. It also induced mitochondrial apoptosis by increasing the expression of Bax, caspase-9, and poly(ADP-ribose) polymerase and mitochondrial membrane potential loss and leaks of cytochrome c (Cyt C) from mitochondria in MCF-7 cells and decreasing the expression of mitochondrial Bcl-2. We further demonstrated whether chloroquine (CQ), which inhibits the degradation of autophagosome induced by NBT, affects the proliferation of MCF-7 cells compared with NBT. The experiments inferred that the combination of NBT and CQ significantly promoted MCF-7 cell mitochondria to divide and Cyt C to be released from mitochondria to the cytoplasm, resulting in an increased apoptosis rate. The in vivo experiments showed that NBT inhibited the growth of MCF-7 tumor via the apoptosis pathway, and its effect was similar to 5-fluorouracil.
Highlights
Betulin (BT) (Fig. 1a) is a naturally occurring pentacyclic lupine-type triterpenoid from birch bark extract with potential hepatoprotective[1], anti-inflammatory[2], Official journal of the Cell Death Differentiation AssociationYan et al Cell Death and Disease (2018)9:241HepG 2 and MCF-7 cells, as evidenced in our previous study 15.Apoptosis and autophagy participate in cellular degradation pathways for maintaining cellular homeostasis and are involved in the protection of organisms from cancer[16,17,18].Apoptosis, a major way of killing cancer cells by anticancer agents, includes two kinds of pathways: caspase-dependent and caspase-independent
NBT inhibits the proliferation of cancer cells As seen in Fig. 2a, b, the IC50 values of NBT for HeLa, A549, and MCF-7 were 24.50 ± 2.50, 49.30 ± 7.90, and 10.83 ± 0.54 μM, respectively, for 48 h
We found that NBT, a novel semisynthetic derivative of BT, possesses a potent antiproliferative activity in MCF-7 cells by inducing cell death
Summary
Betulin (BT) (Fig. 1a) is a naturally occurring pentacyclic lupine-type triterpenoid from birch bark extract with potential hepatoprotective[1], anti-inflammatory[2], Official journal of the Cell Death Differentiation AssociationYan et al Cell Death and Disease (2018)9:241HepG 2 and MCF-7 cells, as evidenced in our previous study 15.Apoptosis and autophagy participate in cellular degradation pathways for maintaining cellular homeostasis and are involved in the protection of organisms from cancer[16,17,18].Apoptosis, a major way of killing cancer cells by anticancer agents, includes two kinds of pathways: caspase-dependent and caspase-independent. Autophagy is a conserved process that is involved in turning over organelles, protein degradation, and differentiation[20] It begins with the trimer formation of beclin 1, PI3KC3 (Vps34), and Atg 14, with beclin 1 constantly increasing autophagy-related proteins. P62, a multifunctional protein, combines with ubiquitinated protein and binds to LC3 II proteins to form a complex that is eventually degraded by enzymes in the lysosome when autophagy occurs[23,24]. It is constantly consumed with increasing levels of autophagy. Atg-5, beclin-1, LC 3-II, and p62 are major indicators in the development of autophagy 25,26
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
